1. Field of the Invention
The present invention is directed to iontophoretic drug delivery systems, and more particularly to electrodes having improved current distribution for iontophoretic drug delivery.
2. Background Art
The use of iontophoretic drug delivery systems has been known in the art for several years. Such devices are generally used to deliver a drug to a patient through the patient""s skin or through the patient""s eye. Generally, such devices comprise an electrode assembly (having a negative and positive electrode) and a power source/control module which is attached to the electrode assembly. The power source provides a potential difference between the electrodes, which facilitates the ionization of materials and the delivery of medicament into a patient.
One problem that has been encountered with the electrode assembly is that the electric current has not been spread uniformly across the electrode. In particular, with respect to conventional positive electrodes, as shown in FIG. 10 (prior art), there is a tendency of the electric current ("THgr") to refrain from spreading across the electrode; instead, the electric current is concentrated around the electrode lead (or the input of the electrical current). As such, the ionic reaction in which the electrode participates, occurs only in the regions proximate the lead, and does not reach much of the electrode. In turn, as the electrode region proximate the lead is sacrificed in the reaction, eventually, the region around the lead is fully depleted, and the reaction ceases. Often the reaction ceases because the region around the lead is depleted even though much of the electrode remains operable if the electric current from the lead could extend to those regions of the electrode.
A similar problem can be seen relative to negative electrodes. In particular, as shown in FIG. 18 (prior art), with a conventional electrode, the current (xcex8) is concentrated proximate the electrical lead. As the reaction progresses and only after the negative electrode reacts for a period of time, the reaction spreads as a frontier across the electrode. Over time, the entire electrode is utilized, however it is not uniformly utilized, which leads to current concentrations in portions of the electrode.
Accordingly, it is an object to provide an electrode having a current distribution element which provides improved distribution of current about an electrode.
The invention comprises an electrode for use in an iontophoretic drug delivery apparatus. The electrode comprises at least one first conductive layer of material and at least one dielectric layer of material disposed upon at least a portion of, but less than the entirety of, the at least one conductive layer of material.
In a preferred embodiment, the electrode further comprises at least one second conductive layer of material disposed upon the at least one of the at least one conductive layer of material which remains exposed and the at least one dielectric layer of material.
In another preferred embodiment, the electrode further comprises a lead attachment region. In one such embodiment, the at least one dielectric layer of material extends from the lead attachment region.
In another embodiment, the at least one conductive layer includes a proximal end and a distal end. The at least one dielectric layer extends substantially from the proximal end to the distal end of the at least one conductive layer.
In yet another preferred embodiment, the at least one dielectric layer of material is formed into a substantially contiguous herringbone pattern. In another preferred embodiment, the at least one dielectric layer of material comprises at least one strip. In one such embodiment, the at least one strip includes a distal end, the distal end is configured to include a taper, which, in turn, precludes concentrations of current therearound.
In another embodiment, the conductive layer of material further includes a proximal end and a distal end. In such an embodiment, the pattern comprises a pattern that is substantially symmetrical from the proximal to the distal end of the conductive layer of material about an axis bisecting the conductive layer of material.
In one embodiment, the electrode further includes a substrate associated with the first layer of material.
The invention further comprises an electrode, for use in an iontophoretic drug delivery apparatus, comprising a first conductive layer of material and at least one sacrificial layer of material disposed upon at least a portion of the at least one conductive layer of material.
In one embodiment, the first conductive layer is configured so as to substantially correspond to the dimensions of the at least one sacrificial layer of material. In another embodiment, the first conductive layer of material comprises a pattern. In yet another embodiment, the pattern comprises a plurality of intersecting strips of material. In another embodiment, the pattern comprises a herringbone pattern.
In a preferred embodiment, the electrode further comprises a transitional conductive material positioned between the conductive layer of material and the sacrificial layer of material.
In another preferred embodiment, the electrode further comprises a substrate associated with the conductive layer of material.
In another aspect of the invention, the invention comprises an electrode, for use in association with an iontophoretic drug delivery apparatus, comprising a conductive layer of material and means for substantially distributing current substantially uniformly about the conductive layer of material, upon supplying electrical current to the conductive layer of material.
In a preferred embodiment, the electrode comprises a positive electrode. In such an embodiment, the current distribution means comprises a dielectric layer of material disposed about at least a portion of, but less than the entirety, of the conductive layer of material.
In another such preferred embodiment, the electrode comprises a negative electrode. In such an embodiment, the current distribution means comprises a sacrificial layer of material disposed over at least a portion of the conductive layer of material.
The invention further comprises a method of manufacturing an electrode for use in association with an iontophoretic drug delivery apparatus. The method comprises the steps of providing a substrate; applying a conductive layer of material upon at least a portion of the substrate; and applying a dielectric layer of material upon a portion of, but less than the entirety of the conductive layer of materia.
In a preferred embodiment, the method further comprises the step of associating a lead to the conductive layer of material.
In one another preferred embodiment, the step of applying the dielectric layer comprises the step of extending the dielectric layer of material away from the lead.
In another preferred embodiment, the method further comprises the step of applying at least one conductive layer upon at least one of the exposed conductive layer of material and the dielectric layer of material.
In one embodiment, the step of applying a conductive layer of material comprises the step of printing the conductive layer of material upon the substrate. Similarly, the step of applying a dielectric layer of material may comprise the step of printing the dielectric layer of material upon the substrate.
The invention further comprises a method of manufacturing an electrode for use in association with an iontophoretic drug delivery apparatus. The method comprises the step of providing a substrate; applying a conductive layer of material upon a portion of the substrate; and applying a sacrificial layer of material upon the conductive layer of material.
In a preferred embodiment, the method further comprises the step of associating a lead to the conductive layer of material.
In another preferred embodiment, the method further comprises the step of applying a transition conductive layer after the step of applying a conductive layer of material.
The invention further comprises a method of uniformly distributing current along an electrode. The method comprises the steps of providing a conductive layer of material; associating a lead to the conductive layer of material; applying a dielectric layer of material to a portion of the conductive layer of material; extending away from the lead toward the extremities of the conductive layer of material; applying an electric current to the lead; and distributing the electric current along the conductive layer of material below the dielectric layer of material.